Apparatus for starting and operating electric discharge lamps

ABSTRACT

An electric discharge lamp ballast apparatus employing a high leakage reactance type of transformer with a shell-type magnetic core and with electrical coils wound of turns of generally round insulated wire which is flattened on the sides to form an essentially oblong cross section with the pair of flattened opposed sides extending in an axial direction with respect to the coil and adjacent to the layer insulation of the coil. The beginning turn or turns and the ending turn or turns of the coil not being flattened, such that they form generally round leads for the coil. Round leads for tap connections to be formed intermediate the ends of the coil are formed by a turn or turns of the coil interconnecting adjacent layers of the coil not being flattened.

United States Patent Caltagirone Mar. 7, 1972 [51] Int. Cl.

[ 54] APPARATUS FOR- STARTING .AND

OPERATING ELECTRIC DISCHARGE LAMPS [72] Inventor: Saverio Callagirone,Danville, Ill.

- [73] Assignee: General Electric Company [62] Continuation of Ser. No.11,454, Feb. 16, 1970, abandoned.

[52] US. Cl. ..336/206, 174/1 19 R, 336/223 .1101! 27/28 [58] FieldoiSeareh ..336/l55, 165, 206, 223, 222; 174/119 R, 129, 133

[56] References Cited UNITED STATES PATENTS 2,735,979 2/1956 Coben..336/223 3,237,136 2/19'66 Lord .......336/206X 3,501,728 3/1970Barriball ..336/223X Primary Examiner-Thomas J. Kozma Attorney-John M.Stoudt, Ralph E. Krisher, Jr., Radford M. Reams, Frank L. Neuhauser,Oscar B. Waddell and Joseph B. Forman [57] ABSTRACT An electricdischarge lamp ballast apparatus employing a high leakage reactance typeof transformer with a shell-type magnetic core and with electrical coilswound of turns of generally round insulated wire which is flattened onthe sides to form an essentially oblong cross section with the pair offlattened opposed sides extending in an axial direction with respect tothe coil and adjacent to the layer insulation of the coil. The beginningturn or turns and the ending turn or turns of the coil not beingflattened, such that they fonn generally round leads for the coil. Roundleads for tap connections to be formed intermediate the ends of the coilare formed by a turn or turns of the coil interconnecting adjacentlayers of the coil not being flattened.

10 Claims, 9 Drawing Figures PAIENTEDMAR 1 @912 SHEET 2 [IF 2 FIG-8 LQma I04 INVENTOR. Saver-Io Caltagw ronq At tor/veg.

APPARATUS FOR STARTING AND OPERATING ELECTRIC DISCHARGE LAMPS Thisapplication is a continuation of application, Ser. No. 1 l,454, filedFeb. I6, 1970, now abandoned.

CROSS-REFERENCES TO RELATED APPLICATIONS The following copendingapplications assigned to the same assignee as the present application,are related:

Apparatus for Starting and Operating Electric Discharge Lamps, RichardD. Barriball, Ser. No. 604,417, filed Dec. 23, 1966, now 0.8. Pat. No.3,501,728.

Improved Method and Apparatus for Winding Electrical Coils SaverioCaltagirone, Ser. No. 11,445, filed on Feb. 16, 1970.

Apparatus and Method for Winding Electrical Coils Saverio Caltagirone,Ser. No. ll,456,filed on Feb. 16, 1970.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to apparatus for operating electric discharge lamps and moreparticularly to an improved apparatus employing flattened wire coilshaving cylindrical or round leads.

2. Description of the Prior Art In the shell type of high leakagereactance transformers used in apparatus for starting and operatingelectric discharge lamps, i.e., fluorescent lamps, the coils containingthe various windings are mounted on a center winding leg, and the sideportions of the coils are positioned within the window space providedbetween the outer yoke members of the core and the center winding leg.The window space dimensions of the magnetic core restrict thecross-sectional dimensions of the coil. It will be appreciated that thecross-sectional area of a ballast case cannot exceed certainstandardized cross-sectional dimensions, and thereby a limit is imposedon the cross-sectional dimensions of the core and coil assembly. In viewof these dimensional restrictions, the core and coil assemblies ofballast transformers have a generally elongated configuration.

Coils commonly used in ballast transformers are constructed ofsuperposed layers of insulated circular conductor wire with interleavedlayers of paper layer insulation. The superposed layers of turns areformed by winding the circular conductor wire on a suitable rectangularshaped spool made of kraft paper. The paper spool on which the coilturns are wound serves to insulate the turns from the center winding legof the magnetic core.

In such conventional coils it will be apparent that the window spaceavailable in the core is not efficiently utilized because of thecircular shape of the conductor wire. Thus, there was a need in aballast apparatus for a core and coil assembly that would allow moreconductive material to be used in window space available in a givenmagnetic core design. It was further desirable for better utilization ofthe core window space to replace copper conductor wire with aluminumwire. Also, it was desirable in a ballast apparatus to reduce theballast case temperature.

These objectives were generally realized in accordance with theinvention set forth in the above-mentioned related application,Apparatus for Starting and Operating Electric Discharge Lamps, RichardD. Barriball, Ser. No. 604,417, filed Dec. 23, I966. Briefly, as taughtin this related application, the objectives were realized by winding theelectrical coils of turns of insulated wire flattened on the sides toform an essentially oblong cross section with opposed elongatedinterlayer insulatingportions extending in an axial direction withrespect to the coil and adjacent to the layer insulation of the coil.

However, it has been found that when coils are wound from insulated wireflattened on the sides to form an essentially oblong cross section, thatas the beginning and ending portion of a turn or turns are pulled frombetween the layer insulation to form the coil leads, that kinks areformed where the flattened wire was bent around a comer of therectangular coil form. It was further found that the strength of thewire was greatly reduced at these kinks, presumably due to the stressingof the wire from the flattening, the bending in winding, and the furthertwisting in pulling the wire out to form the coil leads.

After the wire is pulled from the coil to form the coil leads, it mustbe further handled and manipulated in assembling the coil on themagnetic core, and in attaching the coil leads to terminals forelectrically connecting the coil in the apparatus for starting andoperating electric discharge lamps. It was found that the coil leadswould frequently break at the kinks during this handling andmanipulation, thereby either causing the coil to be scraped, or atconsiderable additional expense the coil might be salvaged, if possible,by again extending the lead to its required length by splicing.

SUMMARY OF THE INVENTION Consequently, the object of the invention is toprovide an improved arrangement for extending leads from the coil of acore and coil assembly of a ballast apparatus, wherein the coil is woundof turns of wire flattened on the sides to form an essentially oblongcross section with the pair of flattened sides extending in an axialdirection with respect to the coil and adjacent to the layer insulationof the coil.

In carrying out the object in one fonn, the portion of a turn or turnsof the coil which are to form the leads of the coil are not flattened asare all of the other turns of the coil.

The subject matter which I regard as my invention is particularlypointed out and distinctly claimed in the concluding portion of thespecification. The invention itself, however, together with furtherobjects and advantages thereof, may be best understood by reference tothe following description taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an enlarged sectionalizedview in perspective of a coil assembly embodying a preferred form of theinvention;

FIG. 2 is a magnified view of a cross section of a single conductor wireused in winding the coil assembly shown in FIG. 1;

FIG. 3 is a magnified view of a cross section of conductor wireflattened at four sides that can be used in winding a coil assembly asshown in FIG. 1;

FIG. 4 is a magnified view of a corner portion of a sectionalized coilassembly such as shown in FIG. I, but in accordance with the prior art,and before the coil leads are pulled;

FIG. 5 is a magnified view of a corner portion of the sectionalized coilassembly as shown in FIG. I, but before the coil leads are pulled;

FIG. 6 is a magnified view of a coil lead pulled from a coil assembly ofthe prior art as shown in FIG. 4;

FIG. 7 is a magnified view of a coil lead pulled from a coil assemblyembodying a preferred form of this invention, as shown in FIG. 1;

FIG. 8 is an enlarged plan view of a magnetic core and coil assembly ofthe type in which coil assemblies as shown in FIG. 1 are utilized;

FIG. 9 is a schematic circuit diagram of a ballast apparatus utilizing acore and coil assembly as shown in FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings,and particularly to FIG. I, l have shown therein a view of a coilassembly 2 constructed in accordance with this invention, which isformed of a plurality of superposed layers of insulated conducting wireinterleaved with insulation layers which are wound over an insulatingspool 3. The conductor wire layers 4, 6, 8, l0, l2, l4, and 16 are of agenerally oblong cross-sectional configuration, with at least a pair offlattened opposite sides, as is shown in FIGS. 4 and 5. Insofar as thecoil assembly of the prior art shown in FIG. 4 and the coil assembly ofthe preferred form of this invention shown in FIG. 5 include identicalelements, they will be referred to by the same identifying numerals.Corresponding elements which are not identical will be identified by thesame identifying numerals, primed in FIG. 5. More specifically, theconductor wire has a cross-sectional configuration as shown in FIG. 2.The opposed interlayer insulation portions 18 and 20 as viewed in FIG. 2are formed by flattening a round insulated metallic conductor 22 toprovide the desired flattening ratio (ratio of the transverse length tothe height of the wire cross section). The interconductor insulatingportions 24 and 26 are generally oval in shape and have a thickness thatis slightly greater than the thickness of the interlayer insultingportions 18 and 20.

Wire which is flattened on four sides as shown in FIG. 3 may be used tofurther advantage to improve the space factor in a coil, and theteachings of this invention are equally applicable with either the wireflattened on two sides as shown in FIG. 2, or four sides as shown inFIG. 3. While for ease of illustration, wire flattened on four sides isshown in FIGS. 4 and 5, at the present time wire flattened on only twosides as shown in FIG. 2 would appear to be more feasible from amanufacturing viewpoint, even though the wire flattened on four sideswould yield a better space factor in a coil.

The advantages of forming a coil of the type of this invention offlattened conductor wire is further set forth in the above-mentionedcopending application entitled Apparatus for Starting and OperatingElectric Discharge Lamps, Richard D. Barriball, Ser. No. 604,417 filedDec. 23, 1966, which application is assigned to the same assignee as thepresent application.

The conductor wire layers 4, 6, 8, 10, 12, 14, and 16 are interleavedwith insulation layers 28, 30, 32, 34, 36, 38 and 40 which may in atypical application be formed of vegetable parchment approximately 0.002of an inch in thickness. It will be appreciated that the paperinsulation layers minimize the effect of voltage stress betweenconductor wire layers by providing an insulating barrier between theconductor wire layers. Further, it will be seen that the paperinsulation layers extend beyond the outer turns in each conductor wirelayer. These extensions of the insulation layers provide a spacingbetween the end turns and the adjacent parts of the magnetic corethereby preventing the end turns from grounding by contacting themagnetic core on which the coil is placed. In order to protect the outerconductor wire layer 16 of the coil, multiple insulation layers 40 and42 are provided at the outer surface of the coil assembly 2. Strips ofpressure sensitive tape 44 and 46 prevent the outer insulation layersfrom unraveling.

It will be appreciated that it is necessary to bring leads out from thecoil assembly in order to make electrical connections to the coil. Thus,in the coil shown in FIG. 1 a start lead 48, a tap 50 and a finish lead52 are brought out from one end of the coil. The manner in which theconductor wire for these leads 48, 50 and 52 is provided will beunderstood by making reference to FIGS. 4 and 5. Coils of the type shownherein may be wound on a multiple coil winding machine. In such awinding machine, a plurality of coils such as shown in FIG. 1 are woundin a side by side relationship, on a long insulating tube with commonsheets of layer insulation between the wire layers. As is seen in FIG.1, and in further detail in FIGS. 4 and 5, a margin is provided at eachend of the coil, such that when the plurality of coils wound togetherare cut apart, it is only necessary to cut through the layer insulationand the spool, the wire conductors being spaced from the area to be cut.

In order to provide conductor wire for bringing out coil leads such as48, 50 and 52 shown in FIG. 1, extra conductor wire turns are providedin one or more layers of the coil such that these conductor wire turnsmay be pulled out from between the insulation layers, or in the case ofthe start lead from between the spool 3 and the first insulation layer28. Referring particularly to the prior art coil assembly shown in FIG.4, in order to provide three coil leads 48, 50 and 52 as shown in FIG.1, two additional turns are provided in conductor wire layers 4, I2 and16. The conductor of these additional turns is pulled from between theinsulation layers to extend from the coil as shown in FIG. 1. The twoextra conductors 54 and 56 provided in the first wire layer 4, form astart lead such as that shown as 48 in FIG. 1. To insure that when theconductor turns 54 and 56 are pulled from the first conductor layer toform the start lead 48, that additional turns are not also pulled out,it is a customary practice to anchor the following turns such as 58 and60. For instance, after winding the conductor turns 54 and 56, a pieceof adhesive tape 62 having its adhesive side facing upward, is Iayedover the top of conductor turns 54 and 56, along the right side ofconductor turn 54 and on top of the layer insulation 64 wound over thespool 3. Thereafter the winding is continued, to wind conductor turns 58and 60 over the adhesive tape. After these turns have been wound, butprior to completing the winding of the first conductor layer 4, the tapwhich was laying over conductor turns 54 and 56 is folded back overconductor turns 58 and 60 as shown in FIG. 4. Thereafter the layerinsulation 28 is placed over the first conductor layer 4, and thesucceeding conductor layer 6 wound thereover. Thus, when the conductorturns 54 and 56 are pulled from the left end of the coil to form thestart lead 48 as shown in FIG. 1, the turn 58 will not be pulled out,wherein it will be retained by the adhesive tape anchor 62.

Similarly, extra conductor turns 68 and 70 are provided in winding layer12 to provide a tap connection such as is shown as 50 in FIG. 1. Again,a piece of adhesive tape 71 is placed around the preceding conductorsturns 72 and 74 in winding layer 12 to insure that they are not pulledfrom between the layer insulation with conductor turns 68 and 70.Wherein conductor turn 68 connects with first conductor turn 76 in thefollowing conductor layer 14, an adhesive type anchor 75 is also placedaround conductor turns 76 and 78 to insure that they are not pulled frombetween the insulation layers 36 and 38. In a similar manner adhesivetape anchor 79 secures conductor turns 80 and 82 in the last conductorlayer 16 to prevent their being pulled from between the layer insulationwith conductor turns 84 and 86 which fonn the finish lead 52.

As set forth hereinbefore, when a coil lead is pulled from a coil formedentirely of flattened conductor wire, such as is shown in FIG. 4, kinkswill be formed in the flattened conductor lead as shown at 88, 90 and 92in FIG. 6. One of these kinks will occur at each point where theconductor was bent in winding it in the coil.

Each of these kinks represents a portion of the coil lead which has beento a considerable degree work hardened. In each of these portions somework hardening is contributed by the flattening of the conductor, moreis contributed by the bending in winding the coil, and still more iscontributed by the twisting experienced as the conductor turn is pulledto form the coil lead. Subsequent operations to be performed in theassembly of the coil in a core and coil assembly and, the subsequentmaking of electrical connections to the coil leads subject the kinkssuch as 88, 90, and 92 to further bending stresses, which all toofrequently lead to the breaking of the lead at one of the kinks.

In accordance with this invention, an improved flattened wire coilassembly has been provided which eliminates the frequent breakageproblem of coil leads which have been pulled from between the layerinsulations of the coil. However, the improved flattened wire coilassembly at the same time retains all of the benefits to be gained fromthe use of flattened conductor wire as hereinbefore set forth. Thus, inaccordance with this invention, the extra conductor turns provided inthe various conductor layers to form leads for a coil such as 48, 50 and52 shown in FIG. I, are formed from round wires, while the remainingturns of the coil are formed of the desired flattened wire.

Referring to FIGS. 5 and 7, the improved flattened wire coil assembly ofthis invention will be described. As previously set forth, the samenumerals as were used on FIG. 4 will be used on FIG. 5 to identifyidentical elements of the coil assembly. Where in accordance with thisinvention the elements are not identical, corresponding elements will beidentified with the same numeral primed. In beginning to wind the firstconductor layer 4 of the coil on the layer insulation 64, the first fewconductor turns 54' and 56' which are provided to form the start lead 48of thecoil as shown in FIG. 1, are wound with unflattened roundconductor. At a point just prior to the application of the adhesive tape62 which secures the conductor turns 58 and 60, the wire is flattened,and continues to be flattened as conductor layers 4, 6, 8, l0 and 12 arewound, until just after the adhesive tape anchor 71 is applied to secureconductor turns 72 and 74. After the insertion of the anchor tape 71,the winding of turns 72 and 74 thereover, and the folding back of tape71 over turns 72 and 74, the conductor is no longer flattened, such thatthe turn 68' and 70 which form the tap connection 50, are formed ofround conductor. Just prior to the application of anchor tape 75 underthe conductor forming turns 76 and 78 in wire layer 14, the wire isagain flattened, such that turns 76 and 78 are formed of flattenedconductor. The conductor continues to be flattened throughout thewinding of coil until just after the winding of turns 80 and 82 in theoutermost conductor layer 16, and the folding back of the anchor tape 83over these turns. At this point the conductor is again not flattened,such that the turns 84' and 86' forming finish lead 52 of the coil areformed of round conductor.

With the conductor turns 54', 56', 68, 70, 84 and 86' which form thecoil leads 48, 50 and 52 shown in FIG. 1, formed of round conductor,when these turns are pulled from between the layers of insulation, thecoil leads will be formed of round wire. Thus, the kinks which werepresent in the flattened conductor leads as shown in FIG. 6, will not beformed, but instead the leads will have the appearance of the roundconductor 94 shown in FIG. 7.

It has been found that the breakage of coil leads in subsequent handlingmay be greatly reduced in the manner just described. Therefore, theround coil leads as formed in accordance with this invention are mucheasier to handle in the later assembly of the core and coil assembly andthe connection of the coil leads in the electrical circuit of theballast apparatus.

As embodied in this invention the entire conductor winding of the coilis formed from a single unspliced strand of round conductor. The entirestrand'of round conductor is flattened to be wound in the conductorlayers of the coil, except for those portions which are to form the coilleads. Various arrangements would be possible for forming a continuousstrand of conductive material including longerportions of flattenedconductor material, interspaced'at desired intervals with the roundconductor material for forming the coil leads. However, a coil inaccordance with this invention is most conveniently formed wherein thewire is flattened by a wire flattening mill just prior to its beingwound in the coil on a coil winding machine. In such an arrangement, theoperation of the wire flattening mill is synchronized with the operationof the winding machine, such that the pressure on the winding millrollers which flattens the conductor is released so as to provide theround conductor at the desired intervals for providing the coil leads asshown in FIGS. 1 and 5. Such an apparatus for winding electrical coilsis set forth in my above-mentioned related patent application entitled,Apparatus and Method for Winding Electrical Coils application Ser. No.11,456, filed Feb. 16, 1970.

Referring now to FIGS. 8 and 9, the manner in which a coil assembly suchas shown in FIG. 1 is used in an apparatus for starting and operatingelectric discharge lamps will be described. As shown in FIG. 8, a pairof coil assemblies 102 and 104, constructed in accordance with thisinvention in the manner shown in FIGS. 1 and 5, are utilized in amagnetic core and coil assembly 106. The coil assemblies 102 and 104 aremounted on a magnetic core 108 comprising a pair of outer yoke members110 and 112 and a center winding leg 114 on which the coil assemblies102 and 104 are supported. Core clamps 116 and 118 hold the outer yokemembers 110 and 112 and the center winding leg 114 in assembledrelation. The outer yoke members 110 and 112 and center winding leg 114are formed of stacks of horizontally extending laminations punched fromsheet magnetic material. The core and coil assembly 106 shown in FIG. 8along with other components such as capacitors and resistors areencapsulated in an enclosure to form a ballast apparatus from whichleads extend for connection to a power supply and to fixture terminalsfor energizing gaseous discharge lamps.

Referring now more particularly to the schematic circuit diagramillustrated in FIG. 9, I have identified the core and coil assembly bythe same reference numeral 106. The core and coil assembly and theresistors and capacitors making up the ballast apparatus are shownenclosed in a dashed rectangle 120 which represents the ballast case. Itwill be appreciated that certain connections with coil assemblies, whichare shown schematically in FIG. 9 are made by bringing out start andfinish leads such as 48 and 52 in FIG. 1 to terminal pads. For a moredetailed description of a typical terminal lead arrangement which may beused in making such circuit connections, reference may be had to US.Pat. No. 3,217,278 issued to G. W. Beckes et al., and assigned to theassignee of the present invention.

The parts of the core and coil assembly 106 are shown schematically inFIG. 9 and include the magnetic core 108, a primary winding P, and asecondary winding S, inductively coupled on the magnetic core 106, andcathode heating winding 11,, H and H A pair of input terminals 121 and122 are provided for connection to a suitable alternating power source(not shown) such as a 60 cycle, 120 volt alternating current pp y- 7 Thefluorescent lamps 124 and 126 operated by the ballast apparatus are ofthe rapid start type and are preferably positioned in close proximity toa grounded conductive fixture or plate 128 so that the lamps 124 and 126are disposed in capacitive relationship with respect to the fixture orplate 128. A flux leakage path is generally provided between the primarywinding P, and the secondary winding S, and may be formed throughnonmagnetic material, such as air, or through magnetic material.

Continuing further with the description of the circuit connections, itwill be seen that the cathode heating windings H,, H and H continuallysupply the filaments of fluorescent lamps 124 and 126 with heatingcurrent during operation. Cathode heating winding H,, which is anextension of the primary winding P,, is connected in circuit withfilament 130 by leads 132, and 134. Cathode heating windings H, and H,are connected in circuit with filaments 136, 138 and 140 by leads 142,144, 146 and 148. Cathode heating windings H, and H, are preferablytightly coupled with the primary winding P, and may, if desired, bewound directly over the primary winding.

One end of the secondary winding S, is connected in circuit with theprimary winding P, in autotransformer relationship. The other end of thesecondary winding S, is connected in circuit with the series capacitorC,, which provides a net capacitive reactance in the lamp circuit. Astarting capacitor C is connected across lamp 124 so that the opencircuit starting voltage is initially applied across lamp 126. ResistorsR, and R which shunt the series capacitor C, and the starting capacitorC are bleeding resistors and cause the charge to be bled oh thecapacitors C, and C when the circuit is deenergized.

The advantages of the present invention can be realized in a ballastapparatus for starting and operating a single fluorescent lamp, as wellas for starting and operating two or more fluorescent lamps. Further, itwill be appreciated that the advantages for the present invention can beused with a magnetic core and coil assembly having one or any number ofcoil assemblies.

It should be apparent to those skilled present, the art that while Ihave described what, at present is considered to be the preferredembodiment of this invention in accordance with the Patent Statute,changes may be made in the disclosed apparatus without actuallydeparting from the true spirit and scope of this invention.

What I claim is new and desire to secure by Letters Patent of the UnitedStates is:

l. A coil assembly comprising:

a. a spool of insulating material formed with an axial opening dischargelamp from an alternating current source, said ballast apparatus having amagnetic core and coil assembly with a magnetic core formed oflaminations of magnetic material and including a winding leg, theimprovement comprising at least one coil assembly including:

b. a plurality of turns of conductor wire forming a coil wound on saidspool to form layers of conductor wire, said turns of conductor wirebeing formed from generally cylindrical wire which is flattened on atleast two sides thereof to form an essentially oblong cross section,

c. layers of insulating sheets interposed between layers of saidflattened conductor wire, and

d. at least a portion of a beginning turn in the first layer of saidconductor wire and at least a portion of an ending turn in the lastlayer of said conductor wire not being flattened on at least two sides,such that said portion of a beginning turn and said portion of an endingturn when extended from said first layer and saidlast layer of saidconductor wire form generally cylindrical leads for said coil ofconductor wire.

2. A coil assembly as defined in claim 1 wherein at least a portion of aturn of conductor wire interconnecting adjacent layers of flattenedconductor wire is not flattened on at least two sides, such that said atleast a portion of a turn of conductor wire when extended from saidlayers of said conductor wire forms a generally cylindrical tap lead forsaid coil of conductor wire.

3. In a ballast apparatus for operating at least one electric a. a spoolof insulating material formed with an axial opening and mounted on thewinding leg of the magnetic core for supporting the coil assemblythereon,

b. a plurality of turns of conductor wire forming a coil wound on saidspool to form layers of conductor wire, said turns of conductor wirebeing formed from generally cylindrical wire which is flattened on atleast two sides thereof to form an essentially oblong cross section,

c. layers of insulating sheets interposed between layers of saidflattened conductor wire, and

d. at least a portion of a beginning turn in the first layer of 40 saidconductor wire and at least a portion of an ending turn in the lastlayer of said conductor wire not being flattened on at least two sides,such that said at least a portion of a beginning turn and said at leasta portion of an ending turn when extended from said first layer and saidlast layer of said conductor wire form generally cylindrical leads forsaid coil of conductor wire.

4. The ballast apparatus set forth in claim 3 wherein at least a portionof a turn of conductor wire interconnecting adjacent layers of flattenedconductor wire is not flattened on at least two sides, such that said atleast a portion of a turn of conductor wire when extended from saidlayers of said conductor wire forms a generally cylindrical tap lead forsaid coil of conductor wire.

5. A coil assembly comprising:

a. a plurality of turns of conductor wire forming a coil wound to formlayers of conductor wire, said turns of conductor wire being formed fromgenerally cylindrical wire which is flattened on at least two sidesthereof to form an essentially oblong cross section,

b. at least a portion of a beginning turn in the first layer of saidconductor wire and at least a portion of an ending turn in the lastlayer of said conductor wire not being flattened on at least two sides,such that said portion of a beginning turn and said portion of an endingturn when extended from said first layer and said last layer of saidconductor wire from generally cylindrical leads for said coil ofconductor wire.

6. A coil assembly as defined in claim 1 wherein at least a portion of aturn of conductor wire interconnecting adjacent layers of flattenedconductor wire is not flattened on at least two sides, such that said atleast a portion of a turn of conductor wire when extended from saidlayers of said conductor wire forms a generally cylindrical tap lead forsaid coil of conductor wire.

7. A coil assembly as defined in claim 5, with said turns of conductorwire being formed from generally cylindrical wire which is flattened onat least four sides thereof to form an essentially rectangular crosssection.

8. In a ballast apparatus for operating at least one electric dischargelamp from an alternating current source, said ballast apparatus having amagnetic core and coil assembly with a magnetic core formed oflaminations of magnetic material and including a winding leg, theimprovement comprising at least one coil assembly including:

a. a plurality of turns of conductor wire forming a coil wound to formlayers of conductor wire, said turns of conductor wire being formed fromgenerally cylindrical wire which is flattened on at least two sidesthereof to form an essentially oblong cross section,

b. at least a portion of a beginning turn in the first layer of saidconductor wire and at least a portion of an ending turn in the lastlayer of said conductor wire not being flattened on at least two sides,such that said at least a portion of a beginning turn and said at leasta portion of an ending turn when extended from said first layer and saidlast layer of said conductor wire form generally cylindrical leads forsaid coil of conductor wire.

9. The ballast apparatus set forth in claim 3 wherein at least a portionof a turn of conductor wire interconnecting adjacent layers of flattenedconductor wire is not flattened on at least two sides, such that said atleast a portion of a turn of conductor wire when extended from saidlayers of said conductor wire forms a generally cylindrical tap lead forsaid coil of conductor wire.

10. A coil assembly as defined in claim 8, with said turns of conductorwire being formed from generally cylindrical wire which is flattened onat least four sides thereof to form an essentially rectangular crosssection.

1. A coil assembly comprising: a. a spool of insulating material formedwith an axial opening b. a plurality of turns of conductor wire forminga coil wound on said spool to form layers of conductor wire, said turnsof conductor wire being formed from generally cylindrical wire which isflattened on at least two sides thereof to form an essentially oblongcross section, c. layers of insulating sheets interposed between layersof said flattened conductor wire, and d. at least a portion of abeginning turn in the first layer of said conductor wire and at least aportion of an ending turn in the last layer of said conductor wire notbeing flattened on at least two sides, such that said portion of abeginning turn and said portion of an ending turn when extended fromsaid first layer and said last layer of said conductor wire formgenerally cylindrical leads for said coil of conductor wire.
 2. A coilassembly as defined in claim 1 wherein at least a portion of a turn ofconductor wire interconnecting adjacent layers of flattened conductorwIre is not flattened on at least two sides, such that said at least aportion of a turn of conductor wire when extended from said layers ofsaid conductor wire forms a generally cylindrical tap lead for said coilof conductor wire.
 3. In a ballast apparatus for operating at least oneelectric discharge lamp from an alternating current source, said ballastapparatus having a magnetic core and coil assembly with a magnetic coreformed of laminations of magnetic material and including a winding leg,the improvement comprising at least one coil assembly including: a. aspool of insulating material formed with an axial opening and mounted onthe winding leg of the magnetic core for supporting the coil assemblythereon, b. a plurality of turns of conductor wire forming a coil woundon said spool to form layers of conductor wire, said turns of conductorwire being formed from generally cylindrical wire which is flattened onat least two sides thereof to form an essentially oblong cross section,c. layers of insulating sheets interposed between layers of saidflattened conductor wire, and d. at least a portion of a beginning turnin the first layer of said conductor wire and at least a portion of anending turn in the last layer of said conductor wire not being flattenedon at least two sides, such that said at least a portion of a beginningturn and said at least a portion of an ending turn when extended fromsaid first layer and said last layer of said conductor wire formgenerally cylindrical leads for said coil of conductor wire.
 4. Theballast apparatus set forth in claim 3 wherein at least a portion of aturn of conductor wire interconnecting adjacent layers of flattenedconductor wire is not flattened on at least two sides, such that said atleast a portion of a turn of conductor wire when extended from saidlayers of said conductor wire forms a generally cylindrical tap lead forsaid coil of conductor wire.
 5. A coil assembly comprising: a. aplurality of turns of conductor wire forming a coil wound to form layersof conductor wire, said turns of conductor wire being formed fromgenerally cylindrical wire which is flattened on at least two sidesthereof to form an essentially oblong cross section, b. at least aportion of a beginning turn in the first layer of said conductor wireand at least a portion of an ending turn in the last layer of saidconductor wire not being flattened on at least two sides, such that saidportion of a beginning turn and said portion of an ending turn whenextended from said first layer and said last layer of said conductorwire from generally cylindrical leads for said coil of conductor wire.6. A coil assembly as defined in claim 1 wherein at least a portion of aturn of conductor wire interconnecting adjacent layers of flattenedconductor wire is not flattened on at least two sides, such that said atleast a portion of a turn of conductor wire when extended from saidlayers of said conductor wire forms a generally cylindrical tap lead forsaid coil of conductor wire.
 7. A coil assembly as defined in claim 5,with said turns of conductor wire being formed from generallycylindrical wire which is flattened on at least four sides thereof toform an essentially rectangular cross section.
 8. In a ballast apparatusfor operating at least one electric discharge lamp from an alternatingcurrent source, said ballast apparatus having a magnetic core and coilassembly with a magnetic core formed of laminations of magnetic materialand including a winding leg, the improvement comprising at least onecoil assembly including: a. a plurality of turns of conductor wireforming a coil wound to form layers of conductor wire, said turns ofconductor wire being formed from generally cylindrical wire which isflattened on at least two sides thereof to form an essentially oblongcross section, b. at least a portion of a beginning turn in the firstlayer of said conductor wire and at least a portion of an endIng turn inthe last layer of said conductor wire not being flattened on at leasttwo sides, such that said at least a portion of a beginning turn andsaid at least a portion of an ending turn when extended from said firstlayer and said last layer of said conductor wire form generallycylindrical leads for said coil of conductor wire.
 9. The ballastapparatus set forth in claim 3 wherein at least a portion of a turn ofconductor wire interconnecting adjacent layers of flattened conductorwire is not flattened on at least two sides, such that said at least aportion of a turn of conductor wire when extended from said layers ofsaid conductor wire forms a generally cylindrical tap lead for said coilof conductor wire.
 10. A coil assembly as defined in claim 8, with saidturns of conductor wire being formed from generally cylindrical wirewhich is flattened on at least four sides thereof to form an essentiallyrectangular cross section.